Mercedes-Benz SL400 Check Engine Light is on Inspection at your home or office.

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Check Engine Light is on Inspection Service

How much does a Check Engine Light is on Inspection cost?

On average, the cost for a Mercedes-Benz SL400 Check Engine Light is on Inspection is $95 with $0 for parts and $95 for labor. Prices may vary depending on your location.

CarServiceEstimateShop/Dealer Price
2016 Mercedes-Benz SL400V6-3.0L TurboService typeCheck Engine Light is on InspectionEstimate$114.99Shop/Dealer Price$132.49 - $145.62
2015 Mercedes-Benz SL400V6-3.0L TurboService typeCheck Engine Light is on InspectionEstimate$94.99Shop/Dealer Price$112.52 - $125.67
Show example Mercedes-Benz SL400 Check Engine Light is on Inspection prices

The Check Engine Light can be one of the most confusing warnings in your dashboard cluster because it offers no explanation as to why you suddenly need to check your engine. It sounds ominous and can be as serious as a malfunctioning catalytic converter or as trivial as a loose gas cap.

How this system works:

The Check Engine Light location and color will vary by vehicle, but in most cases it is a dashboard warning light that is yellow and shaped like an engine. It may or may not have the word “check” integrated into the design.

This indicator is part of the onboard diagnostics (OBD-II) system and in all cases it indicates a problem with your emissions system. Basically, it is an emissions monitoring system. A Check Engine indicator will stay solid or blink.

  • If the indicator is blinking, the situation is usually serious, such as a severe misfiring of the engine. This would allow unburned fuel to dump into the exhaust system, pushing the temperature of your catalytic converter to the breaking point. Slow the car down, find a safe place to stop, and request a mechanic to perform a diagnosis.

  • A steady light on the other hand is not an emergency situation. You can continue driving, but you should schedule an appointment with a mechanic as soon as possible.

Common reasons for this to happen:

While a Check Engine Light can come on for a number of reasons, in most cases it is due to one of the following issues:

  • Loose or damaged gas cap: It’s hard to believe that a gas cap can prompt your check engine light to come on, but it can. Your gas cap acts as the seal for your fuel system and it helps maintain the pressure in your fuel tank. A loose or damaged cap can reduce your gas mileage and increase emissions from your car.

When that annoying yellow light pops on, the first thing you should do is pull over and inspect your gas cap. If it is loose, a quick tighten could very well solve your problem. If it is damaged, head to your local auto parts store for a new one.

Once you have fixed the issue, continue driving to see if the check engine light turns off. If the light stays on, schedule an appointment with a mechanic.

  • Faulty oxygen sensor: An oxygen sensor monitors the exhaust for unburned oxygen, which indicates engine efficacy and the proper air-to-fuel ratio. If you have a faulty sensor, it will not provide the correct data to the onboard computer. The majority of vehicles have two to four sensors. The OBD II code will tell the mechanic which one is giving a reading that is outside of its parameters.

Deterioration of the precious metals inside the oxygen sensor affects the sensors’ ability to give an accurate reading. If you put off getting an oxygen sensor replaced, it will eventually damage your catalytic converter, which can be very costly to replace. Your best bet is to call a mechanic and get a proper diagnosis.

  • Failing catalytic converter: A catalytic converter helps reduce emissions in the exhaust gases. It converts the carbon monoxide and other harmful gases into less harmful emissions. A failing converter will negatively affect your gas mileage and when the damage becomes severe enough, your vehicle won’t go any faster when you push down harder on the gas pedal.

In most cases, a catalytic converter will not fail if you properly maintain your car. A failing converter can be the result of a faulty oxygen sensor that has not been replaced or any other engine efficacy issue.

A broken catalytic converter will eventually bring your car to a complete stop. Before that, your gas mileage will be horrid, the car will not run smoothly, and the car will not pass an emissions test. A damaged converter should be replaced immediately.

  • Faulty mass airflow sensor: This part directs the computer in your vehicle to add the correct amount of fuel based on the air that is coming through the engine. When a mass airflow sensor starts to fail, the car will stall, it will idle poorly, the emissions will go up, and your gas mileage will go down.

An air filter that has never been replaced or improperly installed can sometimes be the culprit when it comes to a faulty mass airflow sensor. Have your air filter checked and replaced on a yearly basis.

While it is possible to drive for months with a malfunctioning mass airflow sensor, it’s not a good idea. Your gas mileage will drop and the car will start stalling frequently. It is best to call a mechanic and have the sensor diagnosed and replaced if necessary.

  • Bad spark plugs and wires: A spark plug acts as a seal in the combustion chamber and provides the gap for the spark that causes combustion in the engine.


While newer cars can go 100,000 miles on a set of plugs, older vehicles, especially those built before 1996, require new plugs roughly every 30,000 miles. There is no way to prevent plugs from failing, it just happens over time. If spark plugs are your issue, get them replaced immediately. A mechanic can make quick work of the job and new plugs in most cases are very affordable.

What to expect:

A top-rated mobile mechanic will come to your home or office to identify the source and cause of the illuminated Check Engine Light, and then check other system components as specific symptoms and issues are identified.

After the inspection, the mechanic will provide a detailed report that describes the diagnosis, along with the scope and cost of the necessary repairs.

How it's done:

When the Check Engine Light is on, your car’s monitoring system will have "fault codes" that indicate the nature of the problem. Your car may have one or more problems and hence there can be multiple codes.

The mechanic will read the codes using a scanner, interpret the codes, and provide a diagnosis. If you approve the repair estimate, they will replace the faulty part(s), clear the memory of any fault codes, turn the Check Engine Light off, and let you drive the car for a few days to see if the light comes back on or not.

Please note: It may take several days of driving the car for the monitoring system to verify that the repair has fixed all the problems. If the monitoring system fails any of its internal tests, it will turn the light back on. This means that the car has more problems that were not evident during the first evaluation. The mechanic will have to perform further diagnosis and create new repair estimates for resolving the problems found. In some rare cases, multiple visits may be required to diagnose and resolve the stubborn Check Engine Light issues.

How important is this service?

A blinking Check Engine Light indicates a critical issue, whereas a solid light reflects a non-emergency situation. Once you rule out a loose gas cap, it’s imperative a mechanic diagnoses the issue as soon as possible.

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Excellent Rating

(262)

Rating Summary
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David

10 years of experience
171 reviews
David
10 years of experience
Mercedes-Benz SL400 V6-3.0L Turbo - Pre-purchase Car Inspection - Orlando, Florida
Pre-Purchase service - On time with appointment. Follow up call and report was generated immediately which is greatly appreciate. Many thanks!!

Enrique

21 years of experience
244 reviews
Enrique
21 years of experience
Mercedes-Benz S550 V8-5.5L - Check Engine Light is on - Davenport, Florida
Enriques was very knowledgeable and professional. He arrived a little early and explained everything I asked him about my vehicle. I would ask for him again.

Charles

27 years of experience
38 reviews
Charles
27 years of experience
Mercedes-Benz GL350 V6-3.0L Turbo Diesel - Check Engine Light is on - Los Angeles, California
Excellent! On time, informative, expert.

Leo

41 years of experience
74 reviews
Leo
41 years of experience
Mercedes-Benz S430 V8-4.3L - Check Engine Light is on - Livermore, California
He is smart, good service ...thumb up for Leo

Excellent Rating

(262)

Rating Summary
241
12
1
0
8
241
12
1
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8
Number of Mercedes-Benz Check Engine Light is on Inspection services completed
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services done by our mechanics
TOTAL NUMBER OF EXPERT Mercedes-Benz MECHANICS
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